Firefox does not prompt for password for http authenticated sites, how to make it prompt?

I'm trying to log in to the corporate intranet. It used to ask me for a password in Firefox.

But suddenly it stopped to do so, and only shows an HTTP 401 Unauthorized error message, just like when you cancel the prompt.

I tried to use livehttpheaders to see if it tries to send wrong credentials but it doesn't send anything in the headers.

Tried the do same on another computer. I got the same headers but it did show the authentication prompt. So I can progress an authenticate.

I tried to delete all history, create a new profile, but no avail.

It works with other browsers and works on another computer on the same operating system with the same version of FF too.

So it seems some of the global settings were screwed up in my FF. Does anybody how can I get my prompt back?

Solution 1:

NTLMv1 authentication has been disabled by default in Firefox 30. To enable, the pref network.negotiate-auth.allow-insecure-ntlm-v1 needs to be set to True. See: https://developer.mozilla.org/en-US/Firefox/Releases/30/Site_Compatibility (down the page under "Security").